Editing FaceBook Login page CSS on Ultimate FaceBook Plugin

Where is the file located that I can edit the styles of the FB Login page? I have a dark theme which it defaults the fonts to white and when I tested the FB Login page after setting it up from the directions, I noticed it defaulted the Login background to white with white fonts, also it’s pulling a menu directory from my website and using it as a header.

I just want a very basic login page for this, where it would just have the basic Facebook signup info and once the user hits submit it will go back to the page, even if the FB login just pops up as a small window on the site.